#include <iostream>
#include <exception>
#include <string>
using namespace std;
int main(){
	string a = "hello world";
	try{
		cout<<a[100];
	}catch(exception e){
		cout<<"不检查越界"<<endl;
	}
	try{
		cout<<a.at(100);
	}catch(exception e){
		cout<<"访问异常"<<endl;
	}
}
